I am confused by this advert. As I understand it the TriVelox C-1 was a conventional pull-chain derailleur that moved the chain sideways over a relatively conventional three speed freewheel. This is not the device shown in the picture.
The TriVelox A-1 was a radical design with a static derailleur-like chain tensioner and a three speed freewheel that was moved side ways by a cable pulling a toggle chain. This is what is shown in the picture.